EP0621843B1

EP0621843B1 - Lockable free wing aircraft

Info

Publication number: EP0621843B1
Application number: EP92925289A
Authority: EP
Inventors: Hugh J. Schmittle
Original assignee: Individual
Current assignee: Individual
Priority date: 1991-11-20
Filing date: 1992-11-20
Publication date: 1999-03-24
Anticipated expiration: 2012-11-20
Also published as: AU3140393A; ATE178006T1; EP0621843A4; EP0621843A1; US5280863A; WO1993010000A1; DE69228762D1

Abstract

The aircraft includes a free wing freely pivotally supported about a spanwise axis for flight in a free wing mode and lockable in selected predetermined, fixed angles of incidence with respect to a fuselage for flight in a fixed wing mode. The predetermined angle of incidence in the fixed wing flight mode is selected to provide sufficient lift for flying the aircraft at low speeds as necessary for takeoff and landing. The aircraft can be converted in flight between the free wing or conventional fixed wing aircraft flight modes. A control system is provided for selectively enabling or disabling the elevators on the horizontal stabilizer and the wing flaps.

Description

The present invention generally relates to an aircraft having a wing free for rotation about a spanwise axis to maintain a constant angle of attack with the relative wind. More particularly, the present invention relates to a wing which is selectively lockable and unlockable relative to the fuselage to enable free rotation of the wing about the spanwise axis, and hence flight in a free-wing mode, and fixation of the wing to the fuselage at a predetermined angle of incidence, and hence flight in a conventional fixed-wing mode.
A "free-wing" is a wing attached to an aircraft fuselage in a manner such that the wing is freely pivotable about its spanwise axis forward of its aerodynamic center. This arrangement enables the wing to have an angle of attack which is determined solely by aerodynamic forces, and therefore, subject only to aerodynamic pitching moments imposed by wing lift and drag. Rotation of the wing, without pilot intervention, induced by positive or negative vertical wind gusts striking the wing causes the angle of incidence or pitch between the wing and the aircraft fuselage to vary so that the wing presents a constant angle of attack to the relative wind enabling the aircraft to be essentially stall-free during flight.
Among other advantages realized when employing a free-wing are increased resistance to stalls, increased C.G. (Center of Gravity) range, alleviation of gust loads, e.g. on the order of a 4:1 reduction, which translates to an increase in passenger comfort of up to 4,000% greater than conventional fixed-wing aircraft, extension of the payload capability due to the ability to reduce the structural weight of the aircraft, and the ability to utilize a smaller engine with a lower fuel requirement, thus increasing the flight range of the aircraft.
Recognizing the advantages associated with free-wings, numerous attempts have been made to adapt the concept of the free-wing to conventional aircraft, particularly in the field of general aviation. However, as discussed below, the free-wing concept has only been successfully applied to light or very light aircraft.
U.S. Patent No. 4,596,368, issued to the present inventor is directed to an ultra-light aircraft wherein a hang cage is suspended from a collapsible Rogallo type-wing by a main hinge assembly. The wing includes a longitudinal keel of light-weight tubular construction, leading edge members, and a cross brace. A flexible lifting panel is secured along and between these members to establish a lifting surface. The hinge is clamped to the keel permitting free rotation of the wing about a spanwise axis extending longitudinally through the cross brace.
U.S. Patent No. 4,568,043, also issued to the present inventor, is directed to an ultra-light aircraft of light-weight construction which includes a freely rotating rigid wing from which a hang cage is suspended by a main hinge assembly.
Although the free-wing concept has been successfully applied to ultra-light aircraft by the present inventor and to a light plane water-borne aircraft, the application of the free-wing concept to conventional aircraft, particularly in the field of general aviation, has not been successfully achieved due to the fact that not only is drag increased as a consequence of the flap deflection needed to properly vary the coefficient of lift of the wing, but in addition, deploying flaps on a free-wing can induce instability of the wing by changing the pitching moment of the airfoil from a positive value, needed for stable free-wing flight, to a negative value. This characteristic of free-wings becomes particularly significant when an aircraft is on final approach and/or during takeoff, as can readily be appreciated by those familiar with the handling of aircraft in flight.
Aircraft such as ultra-lights can ignore the problem associated with low wing lift coefficient, because they are inherently so low wing loaded that they can fly at speeds slow enough to take off and land safely. However, without some method of inducing a free-wing into higher lift coefficients than possible in the pure free-wing, larger size free-wing aircraft are not easily attainable.
Solutions proposed and explored in NASA-funded studies include (i) using leading edge slats instead of trailing edge flaps and (ii) using a free-wing free-trimmer, a device resembling a canard surface protruding from the wing ahead of the leading edge, supported by booms, as well as an alternative version of the free-wing free-trimmer, in which the control surfaces were moved from the canard position to a trailing edge location.
The proposed use of leading edge slats was determined to be structurally over-complicated and otherwise did not provide the required lift coefficient additive. The proposed use of a free-wing free-trimmer was the subject of two further NASA-funded studies. In one of these further studies, NASA CR-2946, Analytical Study of a Free-Wing/Free-Trimmer Concept (1978), it was found that while there was some additional lift force possible with aft mounted trimmers, they required additional mass penalty to balance the free-wing about its hinge line. Moreover, it was found that while forward mounted (canard) trimmers would themselves serve as the required counterweight, they also counteracted the gust alleviation qualities of the free-wing to the extent that such a free-wing would provide an even rougher ride in turbulence than its conventional counterpart, thus destroying one of the desired benefits of the free-wing.
A number of U.S. patents involving free-wing and free-wing-like designs have issued. For example, U.S. Patent No. Re. 18,181 to Stelzer discloses a type of free-wing which includes a means to provide elastic shock absorption.
U.S. Patent No. 3,415,469 to Spratt, builder of the aforementioned aircraft, discloses a free-wing type aircraft in which the pitch of the wing is controlled by the pilot through control stick 46 or control wing 31. In operation, control rods 42 and 43 impart a torque about the wing hinges such that the wing assumes a higher angle of attack while still remaining largely free to rotate in response to gusts.
U.S. Patent No. 4,124,180 to Wolowicz discloses a free-wing aircraft which incorporates a trimmable free stabilizer comprising a floating canard mounted on a strut rigidly connected to the free-wing.
U.S. Patent No. 3,477,664 to Jones discloses a sailplane which uses a flutter wing type in order to enable a self-adjusting angle of attack. The wing is thereby connected to a dashpot mounted inside the fuselage. During flight, the angle of attack can only be adjusted with respect to the present aerodynamic forces, thus, the pilot cannot actively choose a desired angle of incidence.
U.S. Patent No. 3,795,373 to Gerad discloses an aircraft which incorporates a wing comprising flaps mounted on protruding strut elements at the rear of the flying surface. By means of adjusting the relative position of these flaps the airfoil can be balanced in relation to the relative wind after the fashion of a weathercock. Again, the pilot cannot actively predetermine the angle of attack irrespectively of the present aerodynamic flow conditions.
The present invention involves a revolutionary new approach to the problem of how to incorporate the free-wing concept to aircraft of any size, whereas the angle of attack is selectively predeterminable.
Accordingly, it is a primary object of the present invention to provide an improved free-wing aircraft.
It is another object of the present invention to provide an improved free-wing aircraft characterized by a higher lift coefficient during periods of slow flight.
It is a further object of the present invention to provide a free-wing aircraft having a free-wing which is selectively lockable in a fixed angle of incidence to provide a fixed-wing flight mode and unlockable to provide a free-wing flight mode.
A still further object of the present invention is to provide a means for locking a free-wing in a selective fixed angle of incidence.
Yet another object of the present invention is to provide free-wing locking means which allows a higher fixed-wing angle of incidence than is possible in a conventional fixed-wing aircraft so that desired short-takeoff-and-landing (STOL) characteristics may be obtained without degrading the aircraft's high speed flight characteristics.
A still further object of the present invention is to provide an aircraft which selectively operates as either a conventional fixed-wing aircraft or as a free-wing aircraft.
It is yet a further object of the present invention to provide an aircraft which can selectively be transformed into an aircraft for flight in a free-wing mode and into an aircraft for flight in a conventional fixed-wing mode irrespectively of the existing aerodynamic forces, thereby going through intermediate positions.
These objects are solved by the teaching contained in the characterising portion of claim 1.
In accordance with the present invention there is provided an aircraft having the features according to claim 1.
In an embodiment according to the present invention the locking means includes positioning means connected to said wing and a length link pivotally connected to said fuselage and cooperating with said positioning means to enable transition between a first postition wherein said length link does not transfer any forces between said fuselage and said wing thus establishing a free-wing mode of aircraft operation, and second positions wherein said length link locks said wing to said fuselage in a predetermined angle of incidence thus establishing a fixed-wing mode of aircraft operation.
In a further embodiment according to the present invention the locking means further comprises a damper for damping the pivotal movement of said wing relative to said fuselage.
In a preferred embodiment of the present invention this damper is a fluid actuated cylinder comprising a movable piston and a piston rod thus establishing a variable length link.
In accordance with another aspect of the present invention, there is provided a control system for disengaging the elevators of the horizontal stabilizer, while maintaining control of the wing flaps while operating in a free-wing flight mode. Conversely, the wing flaps may be disengaged and the elevators engaged when the aircraft is operating in the fixed-wing flight mode.
In contrast to previous attempts aimed at modifying free-wing aircraft to provide greater lift coefficients by adapting various structural devices to the free-wings, the present invention provides apparatus for effectively transforming a free-wing aircraft into a conventional fixed-wing aircraft and vice versa, and for controlling the aircraft suitably for effecting this transformation. Thus, according to the present invention, the pilot of an aircraft employing the present invention can effectively transform the aircraft to a fixed-wing aircraft in order to provide necessary lift coefficients at slower speeds, e.g., takeoff and landing, corresponding to those required by conventional fixed-wing aircraft. Likewise, once the aircraft is airborne, the pilot can effectively transform the aircraft into a free-wing aircraft so as to incorporate the above enumerated and other advantages associated with free-wings.
These and further objects and advantages of the present invention will become more apparent upon reference to the following specification, appended claims and drawings.
The present invention will hereafter be described with reference to the annexed drawings, which are given by way of non-limiting examples only. Throughout the drawings, like elements are identified by similar reference numerals. In the drawings:
Figure 1 is a perspective schematic view of an aircraft employing a free-wing locking device according to the present invention;
Figure 2 is a fragmentary enlarged side elevational view of the aircraft of Figure 1 illustrating the free-wing locking device thereof;
Figure 3 is a rear schematic cross-sectional view thereof taken about on line 3-3 of Figure 2;
Figure 4 is an enlarged schematic view of the free-wing locking device depicted in Figure 1 and illustrating the geometry of the device in its unlocked condition:
Figure 5 is a view similar to Figure 4 illustrating the geometry of the free-wing locking device in its locked condition;
Figure 6 is a side elevational view of an aircraft illustrating a free-wing locking device according to a second embodiment of the present invention;
Figure 7 is a side elevational view of an aircraft employing a free-wing locking device according to a third embodiment of the present invention;
Figure 8 is a fragmentary end elevational view of the embodiment illustrated in Figure 6 as viewed along line 7-7 in Figure 7;
Figure 9 is a perspective view of an aircraft illustrating aerodynamic fairings covering the free-wing locking device;
Figure 10 is a perspective view of aircraft illustrating further variation of locking devices of the present invention;
Figures 11, 12 and 13 - 14 are perspective, end and side elevational views, respectively, illustrating an embodiment of a control mechanism for use with the present invention.
As depicted in Figure 1, aircraft 1 is generally of a conventional design and includes a fuselage 2, tail section 3, wing 4, and engines 5 on opposite sides of the fuselage. According to the present invention, wing 4 is a free-wing to which is attached a locking means 6 shown schematically. Although Figure 1 depicts an embodiment of the present invention in which the locking means 6 is located above the wing 4, it will become clear as the description of the present invention unfolds, that the locking means 6 could easily be located below the wing 4.
The present invention makes use of a conventional free-wing design wherein the wing 4 is free to rotate or pivot about its spanwise axis 7 forward of its aerodynamic center AC. In order to transform or convert the aircraft from a free-wing aircraft into a conventional fixed-wing type aircraft, the present invention may provide a device 6 having a locking or motion damping mechanism which, when activated or engaged, provides large forces which must be overcome if the wing is to pivot about axis 7. These forces may be made sufficiently large so that the wing 4 is effectively, if not actually, locked in a predetermined angle of incidence, e.g., an angle of incidence which provides a sufficient lift coefficient for takeoff and/or landing, even of aircraft having high wing loadings. When the locking mechanism 6 is deactivated or in the unlocked position, the wing 4 becomes a pure free-wing for all practical purposes.
In order to avoid departing from the type of conventional operation associated with fixed-wing aircraft, the free-wing locking mechanism 6 is designed so that it may be activated simultaneously while activating conventional flaps 12 and elevators 13 which are required for fixed-wing aircraft. Thus, for example, a single control lever or switch 8 may be located in the cockpit which activates and deactivates the free-wing locking mechanism 6 and conventional flaps 12 and elevators 13 which are required for fixed-wing aircraft. This feature is significant since it prevents pilots from having to go through additional and/or unfamiliar or complicated procedures during landings and takeoffs.
A more detailed discussion of the pilot's controls relating the present invention is found hereinbelow. Broadly, apparatus, schematically illustrated at 9 in Figure 1, receives commands from a control stick 10 or other pitch control and the control lever or switch 8 and generates signals 11 to control the position of the flaps 12, elevator 13 and ailerons 14 and the state of the locking mechanism 6, i.e., locked or unlocked. Such apparatus may comprise a processor of the type conventionally used in fly-by-wire control systems or a mechanical connecting apparatus such as the selective coupling apparatus discussed hereinbelow and illustrated in Figures 11 - 14.
As illustrated in Figures 2 and 3, wing 4 is mounted on fuselage 2 by means of elements shown in these Figures so that wing 4 will freely respond to moments applied to the wings about axis 7 in accordance with aerodynamic loading of the wing 4, when in a free wing mode, and those forces, together with other forces generated by the fuselage 2 and control surfaces acting on the wing 4 when operating in a fixed-wing mode. Thus, a wing support bearing 15 mounts the wing spar 16 so that the wing is constrained to a pivoting motion about axis 7 in the free wing flight mode and so that the wing forces of lift, drag, weight, etc., but excluding those forces which may be resolved into a moment acting about wing pivot axis 7, are transmitted from the wing spar 16 through bearing 15 to the fuselage 2. The pivot axis 7 is located with proper consideration to the aerodynamic center of the wing 4 and, as noted above, is preferably located ahead of the wing aerodynamic center AC (Figure 2). There is also provided a wing pivot locking mechanism 6 and aerodynamic control surfaces on the wing 4 such as ailerons 14 and flaps 12 (Figure 1). The angle of the wing 4 at any given instant will be a function of the settings of the control surfaces, the relative wind, the wing inertia and the forces, if any (and ideally none), transmitted from the fuselage 2 through the wing support bearings 15 and wing pivot locking mechanism 6. It will be understood that aerodynamic control surfaces other than flaps 12 and ailerons 14 could be used. Furthermore, it will be apparent that the proportions of the elements in the embodiment shown in the Figures may be varied in accordance with engineering practice and requirements. It would be possible to locate the wing pivot axis 7 relative to the fuselage 2 so that the axis 7 is located in a blister on the fuselage belly, and passes through the lower part of the fuselage 2 as shown in Figures 2 and 3, or the middle of the fuselage 2, etc. It is also possible to locate the pivot axis 7 so that it passes through the top of the fuselage 2 as shown in Figure 6, this being a "high wing" configuration.
The locking means 6 includes a jackscrew and variable length link 17 comprising rod 18 and damper 19 comprised of a fluid, preferably hydraulically, actuated cylinder. The jackscrew comprises a wing mounted motor and rear support 20 which drives and supports a threaded rod 21 onto which an internally threaded shuttle block or traveling nut 22 is threaded. The traveling nut 22 is pivotally joined to rod 18 by ears 23 which extend from nut 22 and a cooperating tang 24 located at the end of rod 18. The ears 23 and tang 24 are connected by a bolt 25 which passes through aligned apertures in the ears 23 and tang 24 and defines a pivot axis 26. The variable length link 17 including rod 18 in turn is connected through damper 19 to a pivot connection on fitting 27 mounted on fuselage 2. A bolt 29 passing through an aperture in a tang 28 affixed to and extending from the end of damper 19 may be screwed into fuselage fitting 27 thus providing a pivot joint between link 17 and fuselage 2. The axis of the pivot joint is identified in Figures 2 and 3 as pivot axis 30.
As will be apparent, actuation of motor 20 will rotate screw 21 causing the shuttle block or traveling nut 22 to travel axially along screw 21. The line of action will be co-linear with the link 17 and thus defined by the line connecting the pivot axes 26 and 30. As will be apparent, the line of action will be pivoted about axis 30 by moving the shuttle block or traveling nut 22.
The significance of shifting this line of action will become apparent by considering Figures 4 and 5 which illustrate the geometry of the various axes and the line of action of the link 17 which are present when the wing locking mechanism 6 is in the unlocked (Figure 4) and locked (Figure 5) positions. In Figure 4, It will be seen that the changes in distance between the two pivot axes 26 and 30 which occur for some particular or prescribed change in wing pivot angle are strongly dependent on the setting of the pivot locking mechanism 6, i.e., the damper 19 elongates and/or shortens much further for a given pivotal movement of the wing 4 when the pivot locking mechanism 6 is in the locked position in comparison to length change of the damper 19 when the mechanism 6 is in the unlocked position. If the damping force is assumed to be proportional to the rate of change of the length of the damper 19, as generally characterizes hydraulic dampers, i.e., hydraulic cylinder/piston assemblies, the damping forces may easily be changed by a factor of 10, 20 or more for a given wing pivot motion by locking or unlocking the pivot locking mechanism 6, assuming the same time is required for executing the prescribed change in wing pivot angle. Since it is the sum of the moments about axis 7 which determines the pivoting motion of wing 4, it is the moment generated by the force acting through the link 17 which needs to be considered when comparing the movement of the wing 4 in the locked and unlocked positions. The geometry indicated in Figure 4 shows that the projected lever arm of the line of action of link 17 about axis 7 is small or even essentially zero when the pivot locking mechanism 6 is unlocked, in contrast to the projected lever when the mechanism 6 is in the locked position. It will thus be seen that the damping moment about axis 7 created by the damper 19 in response to the pivoting movement of the wing may vary greatly: Using the geometry indicated in Figure 5, the damping moment for the wing 4 in the locked position can be easily two orders of magnitude greater than the damping moment for the wing 4 in the unlocked position due to the increased moment arm and increased motion of the damper 19 associated with pivoting motion of the wing 4 when the wing 4 is in the locked position. Ideally, the damping moment in the unlocked condition of the wing 4 is zero.
In Figures 4 and 5, the solid lines indicate the position of various elements when the wing 4 is at one angle of incidence with respect to the fuselage 2 while the dashed lines show the position of the same elements when the wing 4 is at a positive 20 degree angle of incidence with respect to fuselage 2. The relevant positions 26' of pivot axis 26 are shown respectively. Figure 4 shows the free-wing lock mechanism 6 elements disengaged, that is, in the free-wing state, while Figure 5 shows the wing pivot locking mechanism 6 in its wing locked configuration. A comparison of the motion of piston 32 within cylinder 33 of the damper 19 shows the piston motion (d₂) to be significantly greater in the wing locked state for the prescribed 20 degree variation in angle of incidence. It will be understood that a negative change of angle of incidence with respect to the fuselage 2 will also result in less piston motion (d₁) in the unlocked state of Figure 4.
Since the forces acting through the damper 19 will be acting in line with the wing pivot axis 7 when the wing pivot lock mechanism 6 is unlocked, the wing structure and support for the jackscrew must be robust. A support for the end of the screw 21 opposite from the jackscrew motor 20 is conveniently provided by a front bearing 31 (Figure 2).
A selectively actuable positive mechanical lock is incorporated into the damper 19 or otherwise in the link 17 if an infinite damping moment, i.e., a rigid lock, is desired. It will be appreciated that the incompressible fluid used in the cylinder 19 may provide the rigid lock.
Although the positioning means depicted in Figure 2 utilizes a jackscrew mechanism comprising a motor 20 to rotate a threaded rod 21 engaging a threaded shuttle block or traveling nut 22, it will be understood that other known equivalent means might be used, such as, for example, a notched rod or gear rack used in place of threaded rod 21 which rack is engaged by a motor driven spur gear carried on the end of rod 18.
Various devices might be used in place of a simple hydraulic damper such as a damper having characteristics which vary in a predefined and desired manner as a function of the elongation of the damper, a damper having internal valves which are under remote control to vary the damping characteristics, a hydraulic damper combined with a hydraulic cylinder, position locks, springs, etc.. The damper 19 may also be designed to permit "bottoming out" when the damper 19 is at its minimum and/or maximum extension lengths. Means to adjust the length of the rod 18 might also be provided.
In Figure 6 a wing pivoting locking mechanism 6 substantially similar to that depicted in Figure 2 is employed in an aircraft in which the wing 4 is attached on an upper portion of the fuselage 2. The embodiment of the wing pivoting locking mechanism 6 depicted in Figure 6 is essentially the same as that depicted and described in Figures 2-5, the only difference being that the wing pivoting locking mechanism 6 has an orientation which is "upside down,", i.e., inverted, relative to that depicted in Figures 2-5 and is located beneath the wing 4. Otherwise, the elements and operation are essentially the same as discussed above in reference to Figures 2-5.
Figures 7 and 8 show another embodiment of the present invention in which wing 4 is pivotally mounted on pylon 64 which in turn is mounted on and extends upwardly from the fuselage 2. Follower 34 engages and is guided by the slot 35 in sector 36 which is mounted on the fuselage 2. A follower 34 comprises a roller 37 which is mounted on a bolt 38 which bolt is threaded into an extension of the rod 39. The inner radius 40 of the sector 36 is provided with gear teeth 41 which are engaged by spur gear 42. Spur gear 42 is rotationally driven by motor 43, and gear 42 and motor 43 are mounted on the rod 39. It will be seen that the activation of the motor 43 will rotate spur gear 42 causing the rod 39 and the variable length link 44, including damper 45, to rotate about pivot 46.
The path along which follower 34 moves is determined by the shape of slot 35. The path may be selected to provide desirable characteristics to the wing pivoting locking mechanism 6 and may be based on a circle, parabola, hyperbola or any curve deemed desirable. The circular slot path as shown in Figure 7 will provide one particular schedule of change of damping characteristics between the wing locked and wing unlocked positions.
While the discussion of the present invention has been directed to locked and unlocked free-wing operations, it may be desirable to operate a free-wing aircraft with the lock mechanism 6 in an intermediate position under certain flight conditions. In any case, the locking mechanism 6 necessarily passes through intermediate positions in transitioning between the locked and unlocked states and the various elements are designed in consideration of the stresses and conditions that occur throughout the flight.
In order to avoid departing from conventional designs of fixed-wing aircraft, the free-wing locking device 6 is designed to be inconspicuous or otherwise may be concealed by a suitable fairing 47. Thus, Figure 9 is a side elevational view of an aircraft employing a free-wing locking device 6 according to an embodiment of the present invention illustrating an optional fairing or blister 48 on fuselage 2 and fairing 49 on the wing 4 which covers the free-wing locking device 6 and jackscrew respectively. The design of the fairing 47 could obviously be one which blends in with the overall appearance of the aircraft. As shown in Figure 9, a fuselage mounted fairing 48 and wing mounted fairing 49 generally enclose the wing pivot locking mechanism 6. Since the wing 4 and fuselage 2 move relative to each other, the upper and lower fairing portions 48 and 49 will also move relative to each other. The fairings may be designed to have overlapping portions or an elastic web stretched between the fairings so that there will be a continuous aerodynamic surface extending between fairing portions 48 and 49.
Since a free-wing aircraft uses the flaps 12 and/or ailerons 14 on the main wing 4 to control the pivot angle of the main wing 4 and thus control the aircraft lift, it is necessary to provide an alternate means for longitudinal control, e.g., lift control when the wing pivot locking mechanism 6 is engaged. Like conventional aircraft, a free-wing has a horizontal stabilizer 3 to stabilize the fuselage 2 in the air stream. As shown in Figure 1, horizontal elevators 13 are provided in the horizontal stabilizer 3 so that the aircraft pitch may be controlled when the wing 4 is locked.
It is desirable that the elevators 13 be disengaged and locked in position when the wing pivot locking mechanism 6 is unlocked. Figure 1 illustrates a selective coupling apparatus at box 9 which may be used to selectively connect the pitch commands provided by the pilot through the control stick 10 to either the elevator 13 or the flaps 12 in accordance with the setting of the switch or lever 8.
Figures 11 through 14 show an embodiment of a selective connect apparatus 9. In these Figures, pitch command control rod 50 is moved axially in response to control input from pilot lever 10. Rods 51 and 52 are axially moved to control the elevators 13 and flaps 12 respectively in accordance with the setting of the control signal deflection bar 53 which is set by the position of selector rod 54. Plate 55 is provided with an elongated rhomboidal aperture 56 and is mounted on an aircraft frame member 57. A longitudinal slot 58 in the end of control signal deflection bar 53 acts in cooperation with a pin 59 passing through the slot 58 and affixed to a control lever 60 to provide a sliding pivot connection between the control lever 60 and command control rod 50.
Control signal deflection bar 53 is directly mounted by bolt 62 at one end of bar 53 to plate 55 and indirectly to the aircraft frame 57 so that bar 53 may pivot about the axis of bolt 62 in response to the axial motion of transversely oriented selector rod 54. Pitch command control rod 50 is pivotally attached at one end to pin 59 which in turn is mounted on lever 60 so that pitch commands supplied by a pilot and appearing as longitudinal motions of pitch command rod 50 will cause pin 59 to slide along a path determined by slot 58 and move lever 60.
The elevator control rod 51 is pin connected by pin 61 to one end of the control lever 60 while the flap control rod 52 is pin connected by pin 63 to the other end of lever 60. Pins 61 and 63 extend parallel to the axis of sliding pivot bolt 59 and are of sufficient length that they pass through the rhomboidal aperture 56 and extend through the plate 55. Obviously, these pins may engage the edges of aperture 56 when relative movement of the pins 61 and/or 63 bring them into interference with the plate edges represented by the rhomboidal aperture 56. The long axis of the rhomboidal aperture 56 is preferably perpendicular to the axes of the various pins 59, 61 and 63
In operation the position of the signal deflection bar 53 is set by selector rod 54 which is driven by an actuator (not shown) controlled by switch 8. Pilot generated motion of the pitch command control rod 50 will cause the sliding pivot pin 59 of the selector control lever 60 to move along a path defined by the slot 58 in the control signal deflection bar 53. If now the control signal deflection bar 53 is in the position shown in Figure 16, the pin 61 at the end of the selector control lever 60 to which the elevator rod 51 is attached will be located within the acute angle apex of the rhomboidal aperture 56 and unable to move thus fixing the end of the elevator control rod 51 in place and providing a pivot for the selector control lever 60 about pin 61. Any movements imparted to the selector control lever 60 by the pitch command control rod 50 will move the end of the selector control lever 60 to which the flap rod 52 is attached.
Shifting the control signal deflection bar 53 to the opposite position as shown in Figure 13 by means of the selector rod 54 will couple the pitch command control rod 50 to the elevator control rod 51 while holding the flap control rod 52 in a fixed position. Note that pitch command control rod 50 is somewhat flexible to permit the vertical movements of pin 59 which are required.
Consequently, by shifting bar 53 between extreme positions in aperture 56, the wing flaps 12 may be controlled and the elevators 13 disengaged for free wing flight and, conversely, the wing flaps 12 may be locked and the elevators 13 controlled for fixed-wing flight. Of course, in the fixed-wing flight mode, the ability to use the flaps 12 may be retained independently of the aforedescribed control system 9, for example, by a screw-thread vernier system downstream of the aforedescribed control for operating the wing flaps 12 directly.
The apparatus disclosed in Figures 11 - 14 is considered to be only one example of apparatus functioning in a similar manner which might be used. The selector rod 54 may be either driven by an actuator operated by pilot control 8 or a pilot operated lever (also represented by element 8) mechanically connected to the selector rod 54. Other mechanical devices for switching a mechanical input selectively to either of two mechanical outputs might be substituted and the apparatus described above might be modified by shifting the location of the pins on the control lever arm slightly away from the rod attach points, using a rhomboidal aperture having bowed sides, etc.. If the aircraft 1 uses a conventional "fly-by-wire" control system, a simple electrical switch or processor utilizing an appropriate control logic might be used in place of mechanical selective coupling apparatus 9 shown in Figures 11 - 14.
The locking mechanism 6 permits new freedom of aircraft design not heretofore attainable. For example, Figure 10 shows an embodiment where the outer tip portions 91 of the wing 4 comprise a first free-wing lift system, while the inner wing portions 92, that is those portions adjacent to the fuselage 2 on either side, comprise a second free-wing lift system having means to lock the inner wing portions 92 to the fuselage 2 according to the present invention. Further, a simple lock means may be provided to couple the outer and inner free- wing systems 91 and 92 to effectively form a single wing, which is particularly advantageous for high speed flight. The wing mounting system shown in Figure 3, that is, using a bearing 15 supported wing spar 16, would be modified for mounting the wings of this embodiment by means of concentric spars provided with suitable bearings to thereby couple the wing portions making up each of the free-wing systems.
This arrangement has the advantage that the inner free-wing system may be locked so that flaps 90 mounted thereon may be used during low speed flight, as for example takeoff and landing. The outer wing portions 91 may be free during landing, thus providing the desirable characteristics of a free-wing for a major part of the total lift surfaces of the aircraft even during slow speed flight.

Claims

An aircraft comprising:

a fuselage (2);

a wing (4) having an aerodynamic center (AC) and connected to said fuselage for free pivotal movement about a spanwise axis (7) forwardly of said aerodynamic center (AC) thereby establishing a free-wing mode of aircraft operation; and

means (6) for selectively locking said wing (4) at a substantially fixed angle of incidence with respect to said fuselage (2) to thereby terminate said free-wing mode and to selectively establish a fixed-wing mode of aircraft operation during flight
characterised by

said means (6) being adapted for selectively pivoting and actually locking said wing (4) at a predetermined angle of incidence with respect to said fuselage (2) independently of aerodynamic forces acting on the wing.
An aircraft according to claim 1
characterised in that

said locking means (6) includes positioning means connected to said wing (4) and a length link (17) pivotally connected to said fuselage (2) and cooperating with said positioning means to enable transition between a first postition wherein said length link (17) does not transfer any forces between said fuselage (2) and said wing (4) thus establishing a free-wing mode of aircraft operation, and second positions wherein said length link (17) locks said wing (4) to said fuselage (2) in a predetermined angle of incidence thus establishing a fixed-wing mode of aircraft operation.
An aircraft according to claim 2
characterised in that

said positioning means is a screw mechanism comprising a rod (21) carried by said wing (4) and a shuttle block (22) movable along said rod (21), said length link (17) being connected to said shuttle block (22), and means for driving said shuttle block (22) along said rod (21).
An aircraft according to claim 3
characterised in that

said shuttle block (22) includes a threaded bore and said rod (21) is threaded and connected to said threaded bore, said drive means comprising a motor (20) which reversibly rotates said threaded bore.
An aircraft according to claim 3
characterised in that

said positioning means comprises a curved track (35) carried by said fuselage (2) and having an axis non-coincident with said spanwise axis (7), means (34,39) for coupling said wing (4) and said curved track (35) with said coupling means (34,39,) being movable along said track (35), and means (43) for driving said coupling means (34,39) along said curved track (35) to lock said fuselage (2) and said wing (4) at said predetermined angle of incidence.
An aircraft according to one of the foregoing claims
characterised in that

said locking means (6) further comprises a damper (19) for damping the pivotal movement of said wing (4) relative to said fuselage (2).
An aircraft according to claim 6
characterised in that

said damper (19) is a fluid actuated cylinder (33) comprising a movable piston (32) and a piston rod (18) thus establishing a variable length link (17).
An aircraft according to one of the foregoing claims
characterised by

a control system (9) for controlling flaps (12) and elevators (13) on said fuselage (2) and means (8) for disengaging said control system (9).